To a large extent the macromolecular organization and physiological function of connective tissue depends on the selection of the right collagen types. For the normal functioning of connective tissue an exact control of collagen gene expression is therefore required. Studies using cultured skin fibroblasts have already shown that fibroblasts from the involved skin from scleroderma and keloid patients show increased collagen synthesis as compared with those from normal controls. We studied collagen gene expression in dermal fibroblasts from patients with morphea and Werner's syndrome and transformed human fibroblasts. The level of m-RNA for type I collagen in fibroblasts derived from the inflammatory lesion were approximately 60% above those obtained from the normal looking lesion of the skin of a patient with morphea. Increased collagen synthesis accompanying elevated m-RNA levels incultured Werner's syndrome was observed. Decreased type I and type III collagen RNA transcription was observed in transformed human fibroblasts. We also studied collagen metabolism in cutis laxa fibroblasts. And we observed that increased collagenase gene expression associated with unaltered expression of type I and type III collagen.